1. Field of the Invention
The present invention relates to a pneumatic tire, and relates particularly to a design of a sidewall surface of a pneumatic tire.
2. Background Information
In order to improve the fuel efficiency of a vehicle mounted with a pneumatic tire and enhance the maximum speed of a vehicle, the rolling resistance of the pneumatic tire is required to be reduced. In order to reduce the rolling resistance of the pneumatic tire, there have been proposed various embodiments in which the structure of the pneumatic tire, a tread pattern design, and so on are modified.
Further, in order to improve the fuel efficiency of a vehicle and enhance the maximum speed of a vehicle, there has been proposed to reduce the air resistance of a rolling pneumatic tire. The air resistance of the pneumatic tire is affected by unevenness of a tread pattern provided on a surface of a tread portion and unevenness of a mark and a pattern provided on a sidewall surface.
For example, Japanese Patent No. 3028492 describes a pneumatic tire which can reduce air resistance without losing tire performance. In the pneumatic tire, a large number of recesses or protrusions with an equivalent diameter of 3 to 15 mm are distributed on a surface of a sidewall portion all over the circumference. Specifically the recesses or protrusions are provided in a region of at least 10% of the surface area of the sidewall portion on the upper and lower portions in the radial direction around the position of a tire maximum width W.
The recesses or protrusions are intended to cause separation of an air layer on the tire surface move backward as much as possible, whereby generation of a vortex flow is suppressed. Thus, it is regarded that the air resistance in high-speed driving is reduced without losing the tire performance, and the maximum speed of a vehicle can be enhanced.